Synergistic mining method for underground mining, separation and filling for a close distance coal seam group

ABSTRACT

A synergistic mining method for underground mining, separation and filling for a close distance coal seam group is applicable to the mining engineering field. Full-mechanized caving mining is carried out for a close distance coal seam group, an underground coal gangue separation system and a filling face are designed according to the yield of gangue in the production process; the gangue produced in the mining process is transported centrally into an underground coal gangue separation chamber, and the separated gangue is transported to the filling face for filling and mining; the gangue produced at the filling face is transported back to the filling face for backfilling after underground washing separation. The method separates nearby and filling at selected locations, reduces the damage and disturbance to the underground rock mass that may be caused by a conventional mining method, and solves problems in treatment of strong dynamic pressure in advance.

I. CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a national stage entry of international application PCT/CN2018/113556, filed Nov. 2, 2018, the content of which is incorporated herein by reference in its entirety.

II. TECHNICAL FIELD

The present invention generally relates to mining engineering and, more specifically, to a synergistic mining method for underground mining, separation and filling for a close distance coal seam group.

III. BACKGROUND

In the “Safety Regulations in Coal Mine” in China, close distance coal seams are defined as coal seams that are at a close distance from each other and have severe interference with each other during mining. At present, there are 3 ways for mining a close distance coal seam group in China and foreign countries: layer-by-layer upward/downward mining, combined mining, and integrated coal and gangue mining. In a case that the distance between the coal seams is relatively great, utilizing reasonable layer-by-layer upward/downward mining or combined mining can realize stress-relief mining, reduce the interference between upper seam and lower seam during mining, create favorable conditions for subsequent mining, and improve the production efficiency. In a case that the distance between the coal seams is relatively small, especially in a case that the distance between the coal seams is very close, the influence range of utilizing layer-by-layer upward/downward mining or combined mining will be very large, the integrity degree of the roof and floor of the coal seam to be mined next will have been affected by the damage in the mining of the previous coal seam before it is mined; consequently, many new mine pressure phenomena will appear in the mining of the coal seam to be mined next when compared with the case of mining of a single coal seam. In such circumstances, mining of coal seams that are relatively thin is often abandoned in a coal mine, resulting in severe waste of resources. Utilizing full-mechanized caving mining to realize integrated coal and gangue mining can effectively avoid the effects of complex strata behaviors incurred by layer-by-layer mining, improve raw coal recovery ratio by mining the coal seam in entire thickness at one time, and reduce the waste of coal resources; however, a large quantity of gangue may be produced in the production process, which affects coal quality and increases the burden on the main transportation and the main shaft hoisting system. The gangue dump formed by gangue hoisted to the ground surface covers or destroys the vegetation of the original landform; the dust and toxic substances produced in the spontaneous combustion process of gangue and leaching water of gangue that contains heavy metal elements formed in rainfall or spraying causes severe impacts on the living environment of ambient animals and plants. According to the general plan of the state, no permanent surface gangue dump is permitted for any new coal mine, and long-time dumping of solid wastes (e.g., gangue) on the ground is forbidden for existing coal mines. At present, there is no mining method that can realize efficient mining in a close distance coal seam group while avoiding gangue discharge on the ground.

IV. SUMMARY

Technical Problem: In view of the drawbacks in the above-mentioned techniques, the present invention provides a synergistic mining method for underground mining, separation and filling for a close distance coal seam group, which has simple steps, eliminates the adverse impact of surface gangue dump on the environment, improves the clean coal hoisting rate, mitigates the burden on the main hoisting equipment, and employs an approach of separating nearby and filling at selected locations, greatly reduces the damage and disturbance to the underground rock mass caused by a conventional mining method, and solves the difficult problems in treatment of strong dynamic pressure in advance.

Technical Scheme: To attain the above-mentioned technical object, the synergistic mining method for underground mining, separation and filling for a close distance coal seam group according to the present invention comprises the following steps:

-   -   a. designing a fully mechanized caving face, designing a filling         face in an appropriate mining area according to the annual         gangue yield in the mining area, and arranging a sectional         transportation roadway II and a sectional ventilation roadway at         both sides of the filling face;     -   b. designing the size of an underground coal gangue separation         chamber and designing an underground coal gangue separation         system according to the annual yield of gangue in the mining         area, wherein the underground coal gangue separation system         comprises a sectional transportation roadway I in the same         direction as the fully mechanized caving face, the tail end of         the sectional transportation roadway I is connected with the         underground coal gangue separation chamber via a mining area         transportation roadway I, the underground coal gangue separation         chamber is connected with the sectional ventilation roadway via         a gangue concentration roadway arranged below the underground         coal gangue separation chamber, and the underground coal gangue         separation chamber is connected with the sectional         transportation roadway II via the mining area transportation         roadway II;     -   c. mining at the fully mechanized caving face, determining the         mining height and caving height of the coal mining machine         according to the thickness of the close distance coal seam group         and the thickness of the gangue-containing seam, and         transporting the coal gangue produced in the mining process         through the sectional transportation roadway I to the mining         area transportation roadway I;     -   d. transporting the coal gangue through the mining area         transportation roadway I into the underground coal gangue         separation chamber for coal gangue separation, controlling the         obtained gangue to fall into the gangue concentration roadway by         gravity, and finally transporting the gangue to the sectional         ventilation roadway;     -   e. filling and mining the filling face with the coal gangue         transported to the sectional ventilation roadway, determining         the advance rate of the filling face according to the         requirement for the filling rate in the mine, transporting the         coal gangue produced in the mining process at the filling face         through the sectional transportation roadway II to the mining         area transportation roadway II and into the underground coal         gangue separation chamber; then repeating step d;     -   f. repeating steps c, d and e to accomplish the mining in the         entire mining area.

V. BRIEF DESCRIPTION

FIG. 1 shows the synergistic mining method for underground mining, separation and filling of a close distance coal seam group according to the present invention.

In the FIGURES: 1—fully mechanized caving face; 2—sectional transportation roadway I; 3—mining area transportation roadway I; 4—underground coal gangue separation chamber; 5—gangue concentration roadway; 6—mining area transportation roadway II; 7—sectional ventilation roadway; 8—sectional transportation roadway II; 9—filling face.

VI. DETAILED DESCRIPTION

The present invention will be further detailed in an embodiment with reference to FIG. 1.

As shown in FIG. 1, the synergistic mining method for underground mining, separation and filling of a close distance coal seam group in the present invention comprises the following steps:

-   -   a. designing a fully mechanized caving face 1 and designing a         filling face 9 in an appropriate mining area according to the         annual yield of gangue in the mining area, wherein the total         thickness of gangue seams in the close distance coal seam group         in the mining area is not more than 2.0 m, the thickness of each         gangue seam is not more than 1.0 m; some measures may be taken         to the gangue seam according to the actual conditions to         increase the caving property; arranging a sectional         transportation roadway II 8 and a sectional ventilation roadway         7 at both sides of the filling face 9 respectively; the location         of the filling face 9 shall be selected in a mining area where         conditions for fully mechanized caving and integrated coal and         gangue mining in the close distance coal seam group are         unavailable or in a mining area where the distance between the         coal seams in the coal seam group is relatively great and the         coal seam group can be normally mined upward/downward layer by         layer or mined in combination; the annual gangue yield Q is         calculated according to the formula Q=L₁d₁(ρ₁h₁ m₁+ρ₂h₂         m₂)+L₂d₂ρ₁h₃ m₁, where L₁ is the annual advance length of the         fully mechanized caving face 1, d₁ is the width of the fully         mechanized caving face 1, ρ₁ is the apparent density of the         coal, h₁ is the total thickness of the close distance coal seam         group, m₁ is the primary separation rate of gangue from the raw         coal, ρ₂ is the apparent density of the gangue, h₂ is the total         thickness of the gangue seams, m₂ is the primary separation rate         of the gangue, L₂ is the annual advance length of the filling         face 9, d₂ is the width of the filling face 9, and h₃ is the         mining height of the filling face 9; the parameter design of the         filling face 9 is determined according to a formula         Q=L₂d₂h_(c)ρ₂, wherein h_(c) is the fillable height of the         filling face 9;     -   b. designing the size of an underground coal gangue separation         chamber 4 and designing an underground coal gangue separation         system according to the annual yield of gangue in the mining         area, wherein the underground coal gangue separation system         comprises a sectional transportation roadway I 2 in the same         direction as the fully mechanized caving face 1, the sectional         transportation roadway I 2 is equipped with a coal gangue         conveyor belt, the tail end of the sectional transportation         roadway I 2 is connected with the underground coal gangue         separation chamber 4 via a mining area transportation roadway I         3, wherein, the mining area transportation roadway I 3 is         equipped with a coal gangue conveyor belt connected with the         sectional transportation roadway I 2, the underground coal         gangue separation chamber 4 is connected with the sectional         ventilation roadway 7 via a gangue concentration roadway 5         arranged below the underground coal gangue separation chamber 4,         a vertical channel is arranged between the underground coal         gangue separation chamber 4 and the gangue concentration roadway         5, the gangue directly falls onto the gangue conveyor belt         arranged in the gangue concentration roadway 5 by gravity, and         the underground coal gangue separation chamber 4 is connected         with the sectional transportation roadway II 8 via the mining         area transportation roadway II 6, wherein the mining area         transportation roadway II 6 and the sectional transportation         roadway II 8 are equipped with a connected conveyor belt;     -   c. mining at the fully mechanized caving face 1, determining the         mining height and caving height of the coal mining machine         according to the thickness of the close distance coal seam group         and the thickness of the gangue-containing seam, and         transporting the coal gangue produced in the mining process         through the conveyor belt of the sectional transportation         roadway I 2 to the mining area transportation roadway I 3;     -   d. transporting the coal gangue through the conveyor belt in the         mining area transportation roadway I 3 into the underground coal         gangue separation chamber 4 for coal gangue separation,         controlling the obtained gangue to fall into the gangue         concentration roadway 5 by gravity, and finally transporting the         gangue to the sectional ventilation roadway 7;     -   e. filling and mining the filling face 9 with the coal gangue         transported to the sectional ventilation roadway 7, determining         the advance rate of the filling face 9 according to the         requirement for the filling rate in the mine, transporting the         coal gangue produced in the mining process at the filling face 9         through the sectional transportation roadway II 8 to the mining         area transportation roadway II 6 and finally into the         underground coal gangue separation chamber 4; then repeating         step d;     -   f. repeating steps c, d and e, and so on, to accomplish the         mining in the entire mining area.

The location of the filling face shall be selected in a mining area where conditions for fully mechanized caving and integrated coal and gangue mining in the close distance coal seam group are unavailable or in a mining area where the distance between the coal seams in the coal seam group is relatively great and the coal seam group can be normally mined upward/downward layer by layer or mined in combination.

The annual gangue yield Q is calculated according to the formula Q=L₁d₁(ρ₁h₁ m₁+ρ₂h₂ m₂)+L₂d₂ρ₁h₃ m₁, where L₁ is the annual advance length of the fully mechanized caving face, d₁ is the width of the fully mechanized caving face, ρ₁ is the apparent density of the coal, h₁ is the total thickness of the close distance coal seam group, m₁ is the primary separation rate of gangue from the raw coal, ρ₂ is the apparent density of the gangue, h₂ is the total thickness of the gangue seams, m₂ is the primary separation rate of the gangue, L₂ is the annual advance length of the filling face, d₂ is the width of the filling face, and h₃ is the mining height of the filling face.

The parameter design of the filling face is determined according to a formula Q=L₂ d₂h_(c)ρ₂, wherein h_(c) is the fillable height of the filling face.

The total thickness of the gangue seams in the close distance coal seam group involved in the full-mechanized caving mining is not more than 2.0 m, the thickness of each gangue seam is not more than 1.0 m, and appropriate measures may be taken for the gangue seams according to the actual conditions to increase the caving property.

Beneficial Effects:

-   -   1) The method provided in the present invention realizes         underground gangue separation and filling nearby, mitigates the         burden on the main hoisting equipment, saves the hoisting cost         per ton coal and increases the hoisting rate of clean coal;     -   2) The gangue produced in the process of full-mechanized caving         and integrated coal and gangue mining in a close distance coal         seam group is treated properly, the environmental pollution         caused by surface discharge of gangue is eliminated, and green         mining is realized, while the raw coal recovery rate of the         close distance coal seam group is improved;     -   3) Compared with coal pillars, the gangue filling face formed         after filling and mining has the advantages of slow pressure         relief and deformation; thus, the potential safety hazards of         dynamic disasters resulted from the residual coal pillars and         skip-mining can be handled in advance. 

1. A synergistic mining method for underground mining, separation and filling for a close distance coal seam group, comprising the following steps: a. designing a fully mechanized caving face (1), designing a filling face (9) in an appropriate mining area according to the annual gangue yield in the mining area, and arranging a sectional transportation roadway II (8) and a sectional ventilation roadway (7) at both sides of the filling face (9); b. designing the size of an underground coal gangue separation chamber (4) and designing an underground coal gangue separation system according to the annual yield of gangue in the mining area, wherein the underground coal gangue separation system comprises a sectional transportation roadway I (2) in the same direction as the fully mechanized caving face (1), the tail end of the sectional transportation roadway I (2) is connected with the underground coal gangue separation chamber (4) via a mining area transportation roadway I (3), the underground coal gangue separation chamber (4) is connected with the sectional ventilation roadway (7) via a gangue concentration roadway (5) arranged below the underground coal gangue separation chamber (4), and the underground coal gangue separation chamber (4) is connected with the sectional transportation roadway II (8) via the mining area transportation roadway II (6); c. mining at the fully mechanized caving face (1), determining the mining height and caving height of the coal mining machine according to the thickness of the close distance coal seam group and the thickness of the gangue-containing seam, and transporting the coal gangue produced in the mining process through the sectional transportation roadway I (2) to the mining area transportation roadway I (3); d. transporting the coal gangue through the mining area transportation roadway I (3) into the underground coal gangue separation chamber (4) for coal gangue separation, controlling the obtained gangue to fall into the gangue concentration roadway (5) by gravity, and finally transporting the gangue to the sectional ventilation roadway (7); e. filling and mining the filling face (9) with the coal gangue transported to the sectional ventilation roadway (7), determining the advance rate of the filling face (9) according to the requirement for the filling rate in the mine, transporting the coal gangue produced in the mining process at the filling face (9) through the sectional transportation roadway II (8) to the mining area transportation roadway II (6) and finally into the underground coal gangue separation chamber (4); then repeating step d; f. repeating steps c, d and e to accomplish the mining in the entire mining area.
 2. The synergistic mining method for underground mining, separation and filling for a close distance coal seam group according to claim 1, wherein, the location of the filling face (9) is selected in a mining area where conditions for fully mechanized caving and integrated coal and gangue mining in the close distance coal seam group are unavailable or in a mining area where the distance between the coal seams in the coal seam group is great and the coal seam group is be mined upward/downward layer by layer or mined in combination.
 3. The synergistic mining method for underground mining, separation and filling for a close distance coal seam group according to claim 1, wherein: the annual gangue yield Q is calculated according to the formula Q=L₁d₁(ρ₁h₁ m₁+ρ₂h₂ m₂)+L₂d₂ρ₁h₃ m₁, where L₁ is the annual advance length of the fully mechanized caving face (1), d₁ is the width of the fully mechanized caving face (1), ρ₁ is the apparent density of the coal, h₁ is the total thickness of the close distance coal seam group, m₁ is the primary separation rate of gangue from the raw coal, ρ₂ is the apparent density of the gangue, h₂ is the total thickness of the gangue seams, m₂ is the primary separation rate of the gangue, L₂ is the annual advance length of the filling face (9), d₂ is the width of the filling face (9), and h₃ is the mining height of the filling face (9).
 4. The synergistic mining method for underground mining, separation and filling for a close distance coal seam group according to claim 1, wherein, the parameter design of the filling face (9) is determined according to a formula Q=L₂d₂h_(c)ρ₂, wherein h_(c) is the fillable height of the filling face (9).
 5. The synergistic mining method for underground mining, separation and filling for a close distance coal seam group according to claim 1, wherein, the total thickness of the gangue seams in the close distance coal seam group involved in the full-mechanized caving mining is not more than 2.0 m, the thickness of each gangue seam is not more than 1.0 m. 